refactor(ngAria): DRY camelcase method

Author: cironunes

src/ngAria/aria.js

@@ -117,8 +117,8 @@ function $AriaProvider() {
 
 
   function watchExpr(attrName, ariaAttr, negate) {
-    var ariaCamelName = camelCase(ariaAttr);
     return function(scope, elem, attr) {
+      var ariaCamelName = attr.$normalize(ariaAttr);
       if (config[ariaCamelName] && !attr[ariaCamelName]) {
         scope.$watch(attr[attrName], function(boolVal) {
           if (negate) {